Novel CA(1–7)M(2–9) Analogs: Synthesis, Characterization, and Antibacterial Evaluation

Abstract

Hybrid peptides from cecropin A and melittin have attracted the interest of the research community for decades. Here we synthesized several new analogs of the pentadecapeptide CA(1−7)M(2−9) and studied their antibacterial and hemolytic activity and tryptic stability. Single substitution of the Lys residues by Arg did not have a significant impact on the antibacterial activity of these analogs, but the substitution of the five Lys residues by Arg resulted in an increment in hemolytic activity. In contrast, the substitution of Lys residues by Orn conserved the antibacterial activity, with even lower hemolysis, and improved the enzymatic stability. The disulfide cyclic version of CA(1−7)M(2− 9) was obtained by adding a Cys residue to each end of the peptide and carrying out a chemoselective thiol−disulfide interchange using sec-isoamylmecaptan as protecting group of one of these residues. This cyclic peptide showed good antibacterial activity with low hemolysis and improved enzymatic stability.

Secondary Structure Stabilization of Macrocyclic Antimicrobial Peptides via Cross-Link Swapping

“…In this study, lactams between Dap and Glu in analogues 2 , 4 , R2 , and R4 displayed similar CMCs, solubility, and aggregation behavior as parent disulfides 1 and R1 , but lactams between Dab and Glu in analogues 3 , 5 , R3 , and R5 displayed more stable antiparallel β-sheet structures that were more soluble in aqueous solution. Enhanced physiological stability of cyclic peptides, compared with linear analogues, has been documented by others. − Enhanced β-sheet stability may be attributed to enhanced flexibility to minimize steric hindrance within the macrocycle, as previously observed in α-helical peptides, in which longer spacing using Lys and Glu residues stabilized the structure …”

“…Enhanced physiological stability of cyclic peptides, compared with linear analogues, has been documented by others. 47 Enhanced β-sheet stability may be attributed to enhanced flexibility to minimize steric hindrance within the macrocycle, as previously observed in α-helical peptides, in which longer spacing using Lys and Glu residues stabilized the structure. 64 Bacterial uptake of all peptides was not directly related to antibacterial activities.…”

“…The lack of protease stability is a challenging hurdle to surmount for the use of peptides as therapeutic agents. Head-to-tail macrocyclization and disulfide knots have increased peptide stability to enzymatic degradation. − Tryptic stability was determined using TAMRA-labeled peptides that were treated with trypsin in PBS (pH 2) for 30 and 60 min. As a positive control, a TAMRA-labeled HIV-1-derived TAT cell-penetrating linear peptide (YGRKKRRQRRR) was shown by HPLC analysis to be completely degraded after incubation with trypsin for 1 h, as indicated by the peak disappearance and the elution of degradation products after ∼3 min (Figure S29a).…”

Can BioSAXS detect ultrastructural changes of antifungal compounds in Candida albicans?–an exploratory study

“…In addition, it shows pro-inflammatory activity as well as anticancer activity ( Wu et al, 1999 ; Wu and Li, 1999 ). The hybrid peptide from Cecropin A from Hyalophora cecropia (giant silk moth) and Melittin from Apis mellifera (European honey bee), called CA (1–7) M (2–9) has strong antibacterial activity against gram-positive and gram-negative bacteria, follow-up research shows that it is also active against anaerobe species and shows low hemolytic activity (>500 μg/mL) against sheep erythrocytes ( Hultmark et al, 1980 ; Hultmark et al, 1982 ; Andreu et al, 1992 ; Edlund et al, 1998 ; Raghuraman and Chattopadhyay, 2007 ; Chetty et al, 2022 ). The peptide optP7 was obtained from a previously reported peptide library containing 3,000 members to better understand short antimicrobial peptides ( Mikut et al, 2016 ).…”